Mr. Kissinger was so irked by Cuba’s military incursion into Angola that in 1976 he convened a top-secret group of senior officials to work out possible retaliatory measures in case Cuba deployed forces to other African nations, according to documents declassified by the Gerald R. Ford Presidential Library at the request of the National Security Archive, a research group. The officials outlined plans to strike ports and military installations in Cuba and to send Marine battalions to the United States Navy base at Guantánamo Bay to “clobber” the Cubans, as Mr. Kissinger put it, according to the records. Mr. Kissinger, the documents show, worried that the United States would look weak if it did not stand up to a country of just eight million people.